The invention concerns a drive unit for vehicles. The drive unit has an engine and a retarder, wherein the retarder is in constant drive connection with the engine. The coolant in a coolant circuit at the same time comprises the working medium of the retarder, and the retarder can be utilized as a coolant pump. Such a drive unit is known from DE 37 13 580 C1.
While such a drive unit has a number of positive properties, it is solely suited for use at high required overall braking output, notably in sustained braking operation, and with an appropriate expensive configuration, specifically of the retarder and pertaining cooling system.
The problem underlying the invention is to fashion an automotive drive unit wherein, notably in sustained braking operation of a vehicle, a stable braking performance is realized with a concurrent low construction space demand for the individual drive elements, and wherein it is possible to provide a sensitive braking of the vehicle